The Mirror answer is a possibility, but not 100% It would give you some ghosting due to the thickness of glass but that would normally be offset ghosting not vertical esp if you shoting at 45deg. You cant shoot 90 deg at a mirror so the 90deg comment isnt quite right.

Id say a filter, not sure what one but as said a 'fast' or 'speed' type filter, Linear type should give you this, could be just finding the right filter.

Otherwise photoshop it, duplicate layer, motion blur 90deg, by quite a lot then experiment with the opacity and layer mode, poss lighten, overlay or screen at 10% and you'll be pretty similar.

The Mirror answer is a possibility, but not 100% It would give you some ghosting due to the thickness of glass but that would normally be offset ghosting not vertical esp if you shoting at 45deg. You cant shoot 90 deg at a mirror so the 90deg comment isnt quite right.

Id say a filter, not sure what one but as said a 'fast' or 'speed' type filter, Linear type should give you this, could be just finding the right filter.

Otherwise photoshop it, duplicate layer, motion blur 90deg, by quite a lot then experiment with the opacity and layer mode, poss lighten, overlay or screen at 10% and you'll be pretty similar.

I've seen some old mirrors that introduce some serious aberrations especially when off axis, but I'd tend to agree with you that this is not a mirror. This is probably some sort of weird instagram type filter.